Apparatus for measuring density of a thixotropic fluid



Oct. 19, 1948. w. E. BARNES 2,451,605

APPARATUS FOR MEASURING DENSITY OF A THIXOTROPIC FLUID I Filed June 12,1-946 2 Shets-Sheet 1 x 7'0 VACUUM SOURCE I v 41 4 r i; f 3: 40 I. 1":-if go I 44 C i IE: 3= 19 l o 14 5 26-1 2 E? F- I-:- =C P L J:I if a k A46-J- if iii f ji fi i f a m Fig. 1

' INVENTOR WILLIAM E. BARNES @ww w 74 ATTORNEYS w. E. BARNES APPARATUSFOR MEASURING DENSITY OF A THIXOTROPIC FLUID Filed June 12, 1946 2Sheets-Sheet 2 8 All? 0/? GAS I INVENTOR WILLIAM E. BARNES M,WM

ATTORNEYS Patented Qct. 19, 1948 I APPARATUS FOR MEASURING DENSITY OF ATHIXOTROPIC FLUID William E. Barnes, Beaumont, Tex., asslgnor to Sun OilCompany, Philadelphia, Pa., a corporation of New Jersey Application June12, 1946, Serial No. 676,208

i This invention relates to means for determinin v the density of afluid and is particularly adapted for use in determining the density ofa th'ixotropic fluid such as the drilling mud used in the rotarydrilling of wells.

In drilling wells by the rotary method, drilling mud is circulated downthrough the drill pipe and up through the annular space between thedrill pipe and borehole. The mud functions to remove the cuttings fromthe borehole, to prevent caving oi the borehole wall and to providesufflcient hydrostatic pressure to overcome the pressure of theformations penetrated. A close control of the density of the drillingmud throughout the drilling operation is generally highly desirable. Onthe one hand, it is necessary that the weight of the drilling mud besufficient to provide a hydrostatic pressure'adequate to hold backfluids such as gas or water in the formations encountered in order toprevent a blowout of the borehole. On the other hand, if the drillingmud becomes too heavy,

the drilling fluid may be continuously forced into one or more of theformations penetrated resulting in the condition known as lostcirculation." During the course of the drilling frequent adjustment ofthe weight of the mud, as by the addition of weighting materials, isrequired to meet the varying conditions encountered. For instance, uponpenetration of a gas sand, the mud stream may become considerablylighter due to absorption of gas, in which case it is important that thechange in density of the mud fluid be detected immediately so thatproper steps may be takf'en to increase the weight of the circulatingmud and prevent a blowout. In some cases a variation in mud weight ofonly a small fraction of a pound per gallon may be sufficientlyimportant to constitute the difference between satisfactory andunsatisfactory drilling progress. It is evident, therefore, that acontinuous accurate measurement of the mud density during the drillingoperation is highly desirable, v

It is an object of the present invention to provide apparatus forcontinuously measuring the density of a circulating fluid, whichapparatus is designed specifically to operate on a thixotropic fluidsuch as drilling mud and to minimize inaccuracies of measurement tendingto arise as a result of its thixotropic character.

The density measuring apparatus according to the invention utilizes thedifference in pressure on two flexible diaphragms, vertically spacedwithin the fluid. as an indication of the fluid density. While otherdensity measuring devices operating on a similar principle have beenknown heretomg therewith upper and lower sections,

2 Claims. (Cl. 73-32) fore, such devices have not been designed so as toI be capable of accurate measurement when the fluid being measured has athixotropic character, 1. e. the tendency to undergo gelation when quiescent but readily to revert to a fluid state upon agitation. I havefound that density measuring apparatus which includes flexiblediaphragms designed to contact the drilling fluid is apt to be subjectto considerable error of measurement due to gelation of the drillingfluid adjacent the diaphragms.

According to the present invention, such errors in measurement aresubstantially eliminated by providing means for agitating the drillingfluid during its passage through the apparatus and by so positioning theflexible diaphragms as to permit a free flow of fluid across thediaphragms and thereby prevent gelation.

In particular the invention provides apparatus especially adapted foruse where the drilling rig installation has a low substructure. When thedrilling installationis of this typ the drilling fluid returning fromthe well bore issues therefrom at sufllciently low level that thedrilling fluid is not available to flow through'the testing apparatus bygravity. In such cases there is provided as a. part of the apparatusmeans for pumping the drilling-fluid from the mud ditch into theapparatus and simultaneously agitating the drilling fluid within theapparatus to prevent gelation.

For a more complete understanding of the invention reference may be hadto the accompany- Figure 1 shows one form of the device particularlyadapted for use where the drilling rig installation has either a lowsub-structure or no substructure. This form of the device includes meansfor pumping drilling fluid from the mud ditch into the chamber l0. andfor simultaneously agitating the drilling fluid therein to preventgelation. For

this purpose there is provided a diaphragm type pump, indicatedgenerally at 88, comprising upper and lower housing members 40 and 4 I.and flexible diaphragm 42 positioned therebetween and form- The ' lowerhousing member 4| is provided with an inlet including a check valve 43adapted to permit flow of drilling fluid into the lower section of thepump. Valve 43 is connected to drilling fluid sup- 3 ply line 44 whichruns to the mud ditch (not shown). The lower housing member 4| isprovided also with a fluid outlet through which the drilling fluid mayflow into chamber II. A check valve 45 is located in the outlet so as topermit flow only in an outward direction at this point.

Located within chamber In is a stirring-device comprising a rod 48having attached thereto a plurality of fins 41 for agitating the fluidwithin the chamber as the stirring device is caused to reciprocate asdescribed below. The lower end of rod 48 is loosely held in a socket 48fixed to the bottom of the chamber. Toward its upper end rod 46 extendsthrough packing glands 49 and 50 carried respectively by the lower andgland 50 and plate 521s spring 53 which urges diaphragm 42 in a downwarddirection.

A pilot valve 54 is connected to rod 46 near its upper end by means oflink 55. The pilot valve is in communication with a source of vacuumthrough line 56 and with the'upper section of the diaphragm pump throughline 57, and is also provided with a vent shown at 58. The pilot valve,which may be of known design and preferably is of the'snap action type,is adapted to be actuated in accordance with the movement of link 55caused by reciprocation of rod 46. Thus, when rod 48 is at its lowerposition, the upper section of the pump will be connected to the vacuumsource; whereas .when rod 46 is at its upper position, the-upper section-of the pump will be cut oil from the vacuum source and will be open tothe atmosphere through vent 58.

In operating the pump, diaphragm 42 will be urged downward by spring 53until a predetermined lower position is reached at which point pilotvalve 54 will be actuated so as to connect the upper section of the pumpwith the vacuum source. As the upper section is evacuated, diaphragm 42will move upward and, due to closure of check valve 45, will create apartial vacuum in the lower section of the pump, causing drilling fluidto be sucked up from the mud ditch through line 44. When the diaphragmreaches a predetermined upper position, the pilot valve will be actuatedto cut off the vacuum source and to admit air from the atmospherethrough vent 58 and line 51 into the upper section of the pump. Spring53 will then urge the diaphragm downward. Check. valve 43 will closewhile check valve 45 will open, thereby causing drilling fluid to beforced into passageway l0.

When the diaphragm reaches the predetermined lower position, pilot valve54 will again be actuated for evacuation of the upper section of thepump and the operation will be repeated. It may be seen, therefore, thatthe pump will produce a continual flow of drilling fluid from the -mudditch into the apparatus and at the same Figure 2, the pump, comprisingupper and lower housing members 40a and 4m separated by dia- 4 phragm42, is connected with inlet line 44 including check valve 43 and has anoutlet to vertical chamber I0 through check valve 45 all as described inconnection with Figure 1. In this case, however, rod 48a extends throughpacking gland 49a and only up to diaphragm 42 to which it is secured bymeans bf plates Ila and 52a. Spring 58a. is located between packinggland 45a and plate 51a to urge the diaphragm 42 upward. Pilot valve54a, which is oi the same type as described in connection with Figure 1,is located beneath the lower housing member Ma and is attached to rod46a by means Of link 55a for .actuation in accordance with thereciprocal movement of the rod. Air or gas under pressure is supplied tothe pilot valve through line 55a. The pilot valve communicates with theupper section of the pump through line 51a and carries a vent shownas-58a. In this case, when rod 48a is at an upper position, the pilotvalve will connect line 51a to air line 56a and cause air to be admittedto the upper section of the pump thereby forcing the diaphragm, togetherwith rod 46a, downward. When a predetermined lower position is reached,pilot valve 54a will operate to disconnect air line 56a and to connectline 51a with vent 58a thereby relieving the pressure above thediaphragm. Spring 53a will then force the diaphragm and rod 46a to anupper position at which point the pilot valve will again operate toadmit air to the upper section of the pump and repeat the cycle. It isevident that the resulting operation of the pump will serve to pump thedrilling fluid into the apparatus and at the same. time agitate thefluid therein in the same manner as described for Figure 1.

Associated with the passageway or chamber III are a pair of verticallyspaced apart housings Ilia and I51) and two flexible membranes ordiaphragms Ito and 1612 held by the housings. While the housings mayextend within the chamber, if desired, and the diaphragms need notnecessarily be flxed in vertical position, provided the arrangement issuch as to permit substantially unobstructed flow of fluid across eachof the diaphragms, the arrangement illustrated in Figure 1 is preferred.As shown in Figure 1 the housings Ilia and l5b are positioned overopenings in the wall of the chamber i0 and are secured to the wall bymeans of bolts while the diaphragms are anchored between the housing lieand the chamber wall 10. In order to minimize the eflect of the wall asan obstruction to the free flow oi fluid across the diaphragm, the wallthickness should be. small relative to the width of the opening overwhich the diaphragms are positioned, and the edge of the wall around theapertures may be beveled. An overflow line I4 is provided in order tomaintain the level of the liquid in chamber l0 above the upper diaphragml6a.

A difierential pressure indicating device is provided for measuring thedifference in pressures exerted on the diaphragms by the fluid as anindication of the density of the fluid. For this purpose any suitabletype of differential pressure device may be employed. Asdiagrammatically illustrated in Figure l, the device may comprise aU-tube 19 having enlarged section 29 and containing mercury 2|. Thehousings l5a and l5b are in communication with separate legs of theU-tube l9 by means of lines 220. and 22b, respectively. Lines 22a and22b, as well as-thespace enclosed by each of the housings with itsdiaphragm, are fllled with a liquid such as water or oil fortransmitting the pressure exerted by the drilling fluid on eachdiaphragm to the 'difl'erential pressure device. Enlarged section 20 ofthe U-tube contains float "which is adapted to float atthe surface ofthe mercury ll and to rise and tall in accordance with changes in itslevel. Float 23 is connected with scriber-Il through any conventional orsuitable means tor actuating the scriber in accordance with the movementof the float. driven by a clock mechanism and calibrated to show, thedensity 0! the fluid being measured. Numeral 20 indicates an instrumentpanel (shown in broken lines) upon which the diflerential pressureindicating and recording device may be mounted.

What I claim and desire to protect by Letters drilling of a well, wherethe drilling installation is such that the drilling'fluid is normallyunable to flow by gravity from the main fluid stream into the apparatus,which comprises a vertical chamber for the flow of a minor portion ofthe main stream 0! drilling fluid. an inlet adjacent the top and anoutlet adjacent the bottom of the chamber, pumping means for feeding aminor portion of the main stream of drilling fluid through said inletinto the chamber, a pair of cooperating diaphragms positioned atdifferent levels within the chamber and each adapted to be flexed by thepressure of the fluid obtaining in the chamber at its level, agitatingmeans within the chamber,

' said pumping means being arranged to actuate the agitator and preventgelation oi the fluid, a diflerential pressure-indicating device andmeans for transmitting the pressure exerted by the fluid on eachdiaphragm to said device.

2. Apparatus for continuously measuring the density of a circulatingdrilling fluid during the Associated with scriber'fl is chart 2!- in thechamber at the. difl'erent levels, means for maintaining the level ofthe fluid in the chamber above the upper diaphragm, a diaphragm typepump having an inlet in communication with said Number Raine Date1,136,789 Fritchle Apr. 20, 1915 1,878,801 Perkins -a Sept. 1, 19322,115,520 Decker Apr. 28, 1938 2,279,254 Apr. 7, i942 to said device.

WILLIAM E. BARNES.

' ant-nuances crrnn The following referencesare flle of this patent:

UNITED s'ra'ms mum's of record inthe

